Final Paper Home Care Detergent Formulations: Review of the Ingredients and Chemistry of Detergents John Hayes Drexel University- Department of Chemistry Chem 767 Fall 2012 Submitted December 7, 2012
Contents
I. Introduction II. Surfactants III. Builders IV. Enzymes V. Bleaches VI. Additives VII. Conclusion VIII. References
I. Introduction Home Care detergents are primary cleaning products in fabric and dish care. Composition of these detergents consists of several groups of substances. These may include surfactants, builders, enzymes, bleaching agents, and additives/minors such as dispersants, dye transfer inhibiting chemical and optical brightners [1]. The demand of these substances and improvement of the these six categories of substances is a driving force for research and development for new chemicals to replace existing chemical because of environment concerns, lower cost, better performance, or solve performance deficiencies in the detergents [2]. This paper will discuss the six substances in detail.
II. Surfactants Surfactants is an organic chemical that when added to a liquid, changes the properties of that liquid at a surface or interface. The word surfactant stands for surface active agent. Surfactants typically make up about 15% to 40% of the detergent formulation [2]. Surfactants will improve the wetting ability of water [1]. There are two different amphiphilic structures. The surfactants are contains both hydrophilic and lipophilic structure. Hydrophilic, also called oleophobic, with means water-loving [1]. This usually makes up the body of the surfactant. They usually consist of alcohols, ethers, amines, and charged groups [1]. Lipophilic, also called hydrophobic, means oil-loving [1]. They usually consist of long chain aliphatic units without polar atoms or cyclic (can be aromatic or non-aromatic) [1]. The tail is usually composed of lipophilic components [2]. There are 4 types of surfactants. They are anionics, nonionics, cationics, and amphoterics [2]. Each of these structures have the ability to reduce surface tension of a solution, form structures in the bulk of the solution and/or have the ability to modify interfaces by reducing the interfacial tension at the substrate-water and the oil-water interfaces thus allowing for the soil to be removed from the substrate [1]. There are several types of common soils and I am going to describe the two more common types of soils and their removal [1]. First is the oily/greasy soil. The oily/greasy soil typically found on the surface of the material to be cleaned. Surfactants want to absorb by creating a layer at all interfaces [1]. At the edge of the interface between the oily/greasy soil and the solid (material), the surfactant molecules will reduce the contact angle and cause the oil to be pushed off the surface to be suspended, emulsified or solubilized into the cleaning solution [1]. The next soil is the particulate soil [1]. The particulate soil is typically found on the material to be cleaned and also in the wash to be redeposited [1]. Surfactants will also absorb onto the particulate [1]. Surfactants will not only suspend the particulates but they can help prevent the redeposition of the particulate soil back onto the substrate through charge repulsion by giving the soil a negative charge [1].
Now we will discuss the different types of surfactants and examples of each surfactant. Anionic surfactants are the most common surfactant due to low cost and ease of use and incorporation into detergent formulations [2]. The first surfactant was soap [1]. Soap is usually composed of fatty acids such as animal fat or vegetable oil with alkali [1,2]. . Next was alkyl benzene sulfonates but microbes could not break down the branched-chain alkyl benzene sulfonates [2]. The development of the anionic surfactants became more complex as new technology was developed to improve the performance of the surfactant [2]. In the table below, shows an illustration of how surfactants were developed from tallow soap to more complex surfactants such as Linear Alkylbenzene Sulfonate (LAS or LABS) and synthetic alcohol [1, 2].
[Taken from Reference 2] LAS, or LABS, grew more complex and now the linearity of the alkyl chains range from 87% to 98% as seen in Figure below [3]. “While commercial LAS consists of more than 20 individual components, the ratio of the various homologues and isomers, representing different alkyl chain lengths and aromatic ring positions along the linear alkyl chain, is relatively constant in currently produced products, with the weighted average carbon number of the alkyl chain based on production volume per region between 11.7–11.8 has 10 to 14 carbons” [Taken from 3]
[Taken from Reference 3] Anionic surfactants such as LAS are dissociate well in water, make excellent particulate-soil detergents, and have excellent detergency of natural fibers [2,4,5]. Since LAS is a low cost surfactant, LAS has become one of the most common used surfactant in the world in detergents [2, 4]. Some of the drawback of using LAS surfactants is that LAS surfactants are well known to be sequestered and precipitated from the wash solution by divalent cations under high water hardness conditions and thus reduces the cleaning power of the detergent [1]. This is one of the reasons that builders are used to soften the water which will be discussed later in the paper [1]. Another drawback is that LAS is not compatible with enzymes without stabilizers but LAS is compatible with hypochlorite bleach [2]. One route scientists have used to work around this issue is building longer LAS alcohols chains up to C14 -C18 [1]. Another benefit of LAS is that LAS helps with controlling foam and considered a foam stabilizer near neutral or basic pH ranges [4]. LAS have shown some foam control in the presence of lower levels of hardness and in the presence of oily soils [4]. Another anionic surfactant is alcohol sulfates [2, 4]. Alcohol sulfates are high foaming surfactant with excellent detergent properties, compatible with hypochlorite bleach, and hydrolyzes under acidic conditions [4]. Alcohol sulfates are sensitive to hard water and not compatible with enzymes without stabilizers [4]. Alcohol ether sulfates are very good detergents with high foaming surfactant, are milder and more hard water tolerant than LAS and alcohol sulfates, have greater compatibility with enzymes than LAS and alcohol sulfates and have greater versatility [4]. Alcohol ether sulfates are not compatible with hypochlorite bleach [2, 4]. Next surfactant is nonionic surfactants. They have been used in combination with anionic surfactants for many years to combine a boost in performance with keeping cost low [1]. This category of surfactants include alcohol ethoxylate [AE], alkylphenol ethoxylate [APE], methyl ester ethoxylate [MEE], ethoxylated amine, ethoxylated amide, alkyl polyglycoside [APG], polyethylene oxide-polyalkylene oxide diblock copolymer and many others [2, 5, 6]. Nonionic surfactants do not dissociate in solution, are good detergents in removing oily soil, excellent wetting agents, have good hard water tolerance and low to moderate foaming [2, 5, 6]. The most common nonionic surfactant is alcohol ethoxylate [AE]. An AE molecule is comprised of a fatty alcohol, which is ester-linked to polyethylene glycol or ethoxylate chain [5] and the general formula for AE is CH3–(CH2)x–O–(CH2CH2O)y–H [5]. Alcohol ethoxylate has shown that it has a better performance in cleaning the LAS and decent but not great foam control [6]. This is one of the reasons that AE is usually paired with an anionic surfactant typically LAS [1, 2, 6]. Nonionic surfactants are different from anionic surfactants in that the nonionic surfactants are not sensitive to hard water since no precipitation occurs in the presence of divalent ions, typically Ca+ and Mg+ [1, 2, 5, 6]. Next surfactant is the cationic surfactants. Majority of cationic surfactants used in detergent compositions are based on the nitrogen atom carrying positive charge [2]. “The most common cationic surfactants are the quaternary ammonium compounds with the general formula R’R”R’’’R’’’’, where X is usually chloride ion and R represents alkyl groups…, where R contains 8-18 C atoms,” [2]. The quaternary ammonium compounds are used due to the high antistatic activity and thus used as a common fabric softener [2]. It works by reducing the friction between fibers and between fibers and skin. It has been found that addition of certain cationic surfactants has exhibited improved soil and stain removal along with reducing the fading of dyes on colored fabrics [2]. Cationic surfactants will dissociate in water, have good emulsification properties, substantive to surfaces and fibers, have good antistatic properties and are unaffected by water hardness [2. 4, 6] The last surfactant that is mentioned is amphoterics surfactants. Amphoterics surfactant contains both cationic and anionic groups [2]. Amphoteric surfactants will dissociate in water [2]. Amphoteric surfactants are generally moderate to high foamers, excellent oily soil and particulate detergents, and tolerate hard water better than the other surfactans [2]. Most common amphoteric surfactants are N-alkyl betaines such as laurylamidopropyldimethlybetaine. Amphoterics surfactant’s main characteristic is the ability to both cationic and anionic surfactant based on the solution the surfactant is dissolved in [2]. If the specific pH is acidic then the amphoteric surfactant become negatively charged and acts like anionic surfactant while if the specific pH is basic then the amphoteric surfactant becomes positively charged then acts like a cationic surfactant [2]. So this allows the amphoteric surfactants to be highly compatible with other surfactants and stable in both acidic and basic solutions. The detergency of amphoteric surfactants is better than of alcohol ethoxylate on oily soils and has better biodegradability [2, 5, 7]. However the amphoteric surfactants are mild and have lower skin and eye irritation when compared to anionic and nonionic surfactants [7].
III. Builders Builders are called builders because they build the cleaning efficiency and effectiveness of detergent formulations [2]. Builders accomplish the goals of improving cleaning efficiency and effectiveness of detergent formulations by softening the water by binding the hard water minerals [Ca+ and Mg+ are the common minerals] [2, 8, 9, 10, 11] and thus controlling the water hardness [2,9,11]. Builders also help surfactants concentrate on removing soil from fabrics, increase the efficiency of the surfactant, provide a desirable level of alkaline to aid in the cleaning process, and disperse and suspend soils so they cannot redeposit onto the fabrics [2, 9, 11]. Builders have several water softening mechanisms such as sequestration/chelation, precipitation and ion exchange [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Builders can be organic or inorganic in nature [2]. The builder and metal ion form soluble complex such as polyphosphates, EDTA, and polyacrylates and will not interfere with the surfactants from interacting with the soil [2, 9, 11, 12, 13, 14, 15, 16, 17, 18] and thus increasing the efficiency of the surfactants. The builder can form a neutral salt with the metal ion and precipitate out of the solution [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Builder can also be not water soluble and sodium ions are substituted by hard water ions as in the case of zeolites and can sequester the metal ions out of the solution [12, 13]. Builders can act as chelating agents and react with metal ions by sharing electrons to form ringed structures, form highly stable complexes, and control metal ions in aqueous solutions [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Builders, as mentioned earlier, also have the ability to act as a buffer to keep the pH in a desired range to increase the efficiency of the surfactants [2]. Some of the more common builders are sodium carbonate, sodium silicate, sodium metasilicate, potassium silicate, sodium tripolyphosphate (STPP), zeolites A, sodium citrate, EDTA, sodium nitrilotriacetate, dipotassium phosphates, tetrapotassium pyrophosphate, potassium tripolyphosphate, phosphaonates such as Hydroxyethane-diphosphoric acid, and amino-tri(methylenephophonic acid) [9, 11, 12, 13, 14, 15, 16, 17, 18]. Most of these builders have either environmental issues, not biodegradable, or pose toxicity issues [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Polyphosphates have been one of the more common since it has been an effective builder and have very lost cost but there are some environmental issues with phosphates [2, 8, 9, 10]. Polyphosphates tent to precipitate in higher temperatures and used as a softener because of the ability to chelate metal ions out of water very effectively. The environmental concern is that polyphosphates tend to cause eutrophication of waterways and tend to disturb the alkalinity of waterways and thus destroy the habitat of the water when in high concentration [9, 11, 12, 13, 14, 15, 16, 17, 18]. There has been several approaches to replacing the polyphosphates in detergents. Zeolites A have been explored. Zeolites show they can soften the water and demonstrate to not be toxic to the environment [12, 13]. Another substitute builder for polyphosphates is clinoptilolites of western Anatolia [14]. Clinoptilolites show that clinoptilolites can soften water and is comparable to polyphosphates at low temperature washing as a builder [14]. Sodium silicates have also been explored as another alternative to polyphosphate [15]. Amorphous silicate as a builder is comparative in softening water in proving that amorphous silicates have comparable calcium and magnesium tolerance [15]. Silicates as a co-builder in softening water at different temperatures have shown to be very soluble in water [15]. This is useful in assisting in preventing sludge in wastewater [15]. There are also polymeric builders [18]. The use of polyacrylic acid polymers and poly acrylic acid-co-maleic polymers as builders and co-builders to soften the water are being used [18]. They are being looked at as a replacement for polyphosphates in that they are reducing the amount of phosphates entering the waterway [18]. The problem with polymeric builders is that not all the polymers are biodegradable [18]. Research is being constantly done to create a more environmentally safe and more efficient builders to increase the efficiency of the builders and surfactants and increase the effectiveness of the detergents as a primary cleaner. IV. Enzymes Enzymes are a class of proteins present in all living organisms and are used as organic catalysts in such processes like digestion, glycolysis, etc. [19]. Enzymes catalyze a reaction and the reaction most interesting for detergents is hydrolysis [19]. The enzymes are used to break down the different stains and soils into smaller parts, surfactants need to be present to help solubilized the residues [19]. Enzymes are used in detergents to assist on enzyme sensitive stains such as egg yolk, spaghetti sauce, and organic soil [20]. Enzymes-containing products compromise more than 80% of the total laundry market [20]. There are several types of enzymes that are used in detergents. One of the more common enzymes for detergents is protease [21]. Proteases break down protein based soils such as blood, grass, and egg yolk [19, 21]. Another common enzyme for detergents is lipases. Lipases are used to break down fats and oils derived from animals or vegetables [19]. Another enzyme is amylase [19, 21]. Amylases are used to break down starches based on sugars such as chocolate and food syrups [19, 20, 21]. Another common enzyme is cellulose [21]. Cellulases are used to breakdown cellulose and remove microfibrils and polish fabrics [21]. Enzymes do break down and assist in removing soils but there are some drawbacks. Enzymes have a short shelf life [19, 20, 21]. They become inactivated in a short amount of time usually around 6 months or less [21]. Another drawback is that certain surfactants will cause surfactant-induced unfolding of the enzyme [19, 20, 21] and thus make the enzyme useless in the detergent. V. Bleaches Bleaches are chemicals that oxidize or reduce chemical bonds especially in unsaturated bonds that tend to be highly colored [2]. Bleach is used to decolorize stains and soils, kill microbes, and can be used to maintain whiteness [2]. There are two categories for the bleach and bleaching agents in cleaning detergents [2]. There are oxygen bleach and bleaching agents [2]. Oxygen bleach is used in the detergent oxide stains and remove soil. They can be either aqueous or dry [2]. “All dry oxygen bleaches contain inorganic peroxygen compounds, such as sodium perborate tetrahydrate and sodium percarbonate” [Taken from reference 2]. The oxygen bleach provides the detergent more of a gentle bleach cleaner that will decolorize or break up soil and organic materials during the cleaning application. Bleaching agents are used to make white clothes clean and keep them white [2]. The advantage is that this gives the detergent more cleaning power and better performance but the disadvantage is that this could have an effect on clothes with color and allow the colors to fade or be bleached out. VI. Additives Additives are chemicals that are added to give the detergent additional properties, smell, color, buffer, viscosity, and give a aesthetic improvement [2]. One property that is desired that an additive may help with is anti-redeposition [2]. Anti-Redeposition is to prevent soils and stains from redepositing onto the clean surfaces [2]. Anti-redeposition agents will help keep soils and stains suspended in the wash water so that it will not redeposit back on the fabrics or clean surfaces but go with the solution into the waste stream [2]. Several common anti-redeposition agent is anionic polymers, nonionic polymers, sodium polyacrylates, polyethylene glycol and polyacrylic acid [2, 18]. Another additive is a dispersant. Dispersant is used to suspend soils, particles, and metal ions for water hardness [2, 22]. Some builders could be used as a dispersant since they can suspend soils, particles and metal ions [2,21]. The suspension of metal ions will prevent the chemical from being an effective builder but may allow other builders and surfactants to be more effective in cleaning performance [2, 21]. Some additives may be used as buffer [2]. The additive may be used to maintain a certain pH that is optimal for the builder and surfactant to be an effective detergent in cleaning performance [2]. Some additive may be used as a corrosion inhibitor [2]. The additive may be used to prevent corrosion and oxidizing of the clean materials [2]. Some additives may be added to as a processing aid or as a co-polymer to keep the formulation homogenous [2]. Some additives are used as colorants for aesthetic improvement [2]. Fragrances can be added as an additive to improve the smell and create the desired odor [2]. Some additives are added for foam control [2]. Some additives are used as opacifiers to give the formulations a rich, viscous opaque appearance [2]. Other additives are used in specialized way such as optical brightners or a convenience to the customers [2]. VII. Conclusion Home Care Detergents are composed of several different substances and all of the substances bring a unique property to the formulation. Surfactants are used as the primary cleaners in the formulation and are done at the surface or interface with the soil or stain [2]. Builders are used to build the cleaning efficiency and effectiveness of detergent formulations [2]. Enzymes may be used to break down the soils so that the surfactants can suspend the soil or stain. Bleaches used to decolorize stains and soils, kill microbes, and can be used to maintain whiteness [2]. Additives are chemicals that are added to give the detergent additional properties, smell, color, buffer, viscosity, and give a aesthetic improvement [2]. So each substance is used in the detergent to give the best cleaning performance. VIII References:
[1] Baipal, Divya; Tyagi, V.K. [2007] "Laundry Detergents; An Overview" Journal of Oleo Science 56 [7] 327-340 DOI Link
[2] Scheibel, Jeffrey J. [2004] “The evolution of anionic surfactant technology to meet the requirements of the laundry detergent industry” Journal of Surfactants and Detergents 7 [4] 319-328 DOI Link
[3] Sanderson, Hans; Dyer, Scott D.; Price, Bradford B.; Nielsen, Allen M.; Compernolle, Remi van; Selby, Martin; Stanton, Kathleen; Evans, Alex; Ciarlo, Michael; Sedlak, Richard [2006] “Occurrence and weight-of-evidence risk assessment of alkyl sulfates, alkyl ethoxysulfates, and linear alkylbenzene sulfonates (LAS) in river water and sediments” Science of The Total Environment 368 [2-3] 695-712 DOI Link
[4] Zhang, Hui; Miller, Clarence A.; Garrett, Peter R.; Raney, Kirk H. [2005] “Lauryl alcohol and amine oxide as foam stabilizers in the presence of hardness and oily soil” Journal of Surfactants and Detergents 8 [1] 99-107 DOI Lilnk
[5] Belanger, S.E.; Dorn, P.B., Toy, R.; Boeije, G.; Marshall, S.J.; Wind,T.; Compernolle,, R. Van; Zeller, D. [2006] “Aquatic risk assessment of alcohol ethoxylates in North America and Europe” Ecotoxicology and Environmental Safety 64 [1] 85-99 DOI Link
[6] Tamura, Takamitsu; Iihara, Tadashi; Nishida, Shigeo; Ohta, Seiich [1999] “Cleaning Performance and Foaming Properties of Lauroylamidopropylbetaine/Nonionics Mixed Systems” Journal of Surfactants and Detergents 2 [2] 207-211 DOI Link
[7] Wolf M.D., Ronni; Parish M.D., Lawrence Charles [2012] “Effect of soaps and detergents on epidermal barrier function” Clinics in Dermatology 30 [3] 297-300 DOI Link
[8] Diamond, W.J. [1959] “The Effect of Temperature on the Phase Equilibrium of Polyphosphates” J. Phys. Chem 63 [1] 123-124 DOI Link
[9] Shen, C.Y.; Dyroff, D.R. [1966] “Hydrolyic Degradation of Sodium Tripolyphosphate in Concentrated Solutions and in Presence of Foreign Ions” Ind. Eng. Chem. Prod. Res. Dev. 5 [2] 97-100 DOI Link
[10] Scaffer, J.F.; Woodhams, R.T. [1977] “Polyelectrolyte Builders as Detergent Phosphate Replacements” Ind. Eng. Chem. Prod. Res. Dev. 16 [1] 3-11 DOI Link
[11] De Lucas, Antonio; Uguina, M. Angeles; Covian, Ignacio; Rodriguez, Lourdes [1992] “Synthesis of 13X zeolite from calcined koalins and sodium silicate for use in detergents” Ind. Eng. Chem. Res. 31 [9] 2134-2140 DOI Link
[12] Maki, Alan W.; Macek, Kenneth J. [1978] “Aquatic environmental safety assessment for a nonphosphate detergent builder” Environ. Sci. Technol. 12 [5] 573-580 DOI Link
[13] Costa, Enrique; De Lucas, Antonio; Uguina, M. Angeles; Ruiz, Juan Carlos [1988] “Synthesis of 4A zeolite from calcined kaolins for use in detergents” Ind. Eng. Chem. Res 27 [7] 1291-1296 DOI Link
[14] Çulfaz*, Müjgan; Saraçoğlu, Nurdan; Özdilek, Özlem [1996] “Clinoptilolites of western anatolia as detergent builders” Journal of Chemical Technology and Biotechnology 65 [3] 265-271 DOI Link
[15] De Lucas, Antonio; Rodriquez, Lourdes; Sanchez, Paula; Lobato, Justo [2000] “Synthesis of Crystalline Layered Sodium Silicate from Amorphous Silicate for Use in Detergents” Ind. Eng. Chem. Res. 39 [5] 1249-1255 DOI Link
[16] De Lucas, Antonio; Rodriquez, Lourdes, Sanchez, Paula; Carmona, Manuel; Romero, Pedro; Lobato, Justo [2004] “Comparative Study of the Solubility of the Crystalline Layered Silicates α-Na2Si2O5 and δ-Na2Si2O5 and the Amorphous Silicate Na2Si2O5” Ind. Eng. Chem. Res. 43 [6] 1472-1477 DOI LInk
[17] Matsumura, Shulchi; Nishioka, Makoto; Shigeno, Haruo; tanaka, Toshiyuki; Yoshikawa, Sadao [1993] “Builder performance in detergent formulations and biodegradability of partially dicarboxylated cellulose and amylose containing sugar residues in the backbone” Angew. Makromol. Chem 205 [1] 117-129 DOI Link
[18] Marholz, Thorsten; Klein, Joachim; Klein, Thomas [2002] “New Poly(sodium carboxylate)s Based on Saccharides, 1. Synthesis and Characterization of Ionic Allyl Glycoside Polymers” Macromolecular Chemistry and Physics 203 [18] 2640-2649 DOI Link
[19] Lund, Henrik, Kaasgaard, Svend Gunnar; Skagerlind, Peter; Jorgensen, Lene; Jorgensen, Christian Isak; van de Weert, Marco [2011] “Protease and Amylase Stability in the Presence of Chelators Used in Laundry Detergent Applications: Correlation Between Chelator Properties and Enzyme Stability in Liquid Detergents” Journal of Surfactants and Detergents 15 [3] 265-276 DOI Link
[20] Stoner, Michael R.; Dale, Douglas A.; Gualfetti, Peter J.; Becker, Todd; Manning, Mark C.; Carpenter, John F.; Randolph, Theodore W. [2004] “Protease autolysis in heavy-duty liquid detergent formulations: effects of thermodynamic stabilizers and protease inhibitors” Enzyme and Microbial Technology 34 [2] 114-125 DOI Link
[21] Stoner, Michael R.; Dale, Douglas A.; Gualfetti, Peter J. Becker, Todd; Randolph, Theodore W. [2006] “Surfactant-Induced Unfolding of Cellulase: Kinetic Studies” Biotechnology Progress 22 [1] 225-232 DOI Link
[22] Strauss, Ulrich P.; Treitler, Theodore L. [1955] “Chain Branching in Glassy Polyphosphates: Dependence on the Na/P Ratio and Rate of Degradation at 25°“J. Am Chem Soc. 77 [6] 1473-1476 DOI Link
Home Care Detergent Formulations: Review of the Ingredients and Chemistry of Detergents
John Hayes
Drexel University- Department of Chemistry
Chem 767 Fall 2012
Submitted December 7, 2012
Contents
I. Introduction
II. Surfactants
III. Builders
IV. Enzymes
V. Bleaches
VI. Additives
VII. Conclusion
VIII. References
I. Introduction
Home Care detergents are primary cleaning products in fabric and dish care. Composition of these detergents consists of several groups of substances. These may include surfactants, builders, enzymes, bleaching agents, and additives/minors such as dispersants, dye transfer inhibiting chemical and optical brightners [1]. The demand of these substances and improvement of the these six categories of substances is a driving force for research and development for new chemicals to replace existing chemical because of environment concerns, lower cost, better performance, or solve performance deficiencies in the detergents [2]. This paper will discuss the six substances in detail.
II. Surfactants
Surfactants is an organic chemical that when added to a liquid, changes the properties of that liquid at a surface or interface. The word surfactant stands for surface active agent. Surfactants typically make up about 15% to 40% of the detergent formulation [2]. Surfactants will improve the wetting ability of water [1]. There are two different amphiphilic structures. The surfactants are contains both hydrophilic and lipophilic structure. Hydrophilic, also called oleophobic, with means water-loving [1]. This usually makes up the body of the surfactant. They usually consist of alcohols, ethers, amines, and charged groups [1]. Lipophilic, also called hydrophobic, means oil-loving [1]. They usually consist of long chain aliphatic units without polar atoms or cyclic (can be aromatic or non-aromatic) [1]. The tail is usually composed of lipophilic components [2]. There are 4 types of surfactants. They are anionics, nonionics, cationics, and amphoterics [2]. Each of these structures have the ability to reduce surface tension of a solution, form structures in the bulk of the solution and/or have the ability to modify interfaces by reducing the interfacial tension at the substrate-water and the oil-water interfaces thus allowing for the soil to be removed from the substrate [1]. There are several types of common soils and I am going to describe the two more common types of soils and their removal [1]. First is the oily/greasy soil. The oily/greasy soil typically found on the surface of the material to be cleaned. Surfactants want to absorb by creating a layer at all interfaces [1]. At the edge of the interface between the oily/greasy soil and the solid (material), the surfactant molecules will reduce the contact angle and cause the oil to be pushed off the surface to be suspended, emulsified or solubilized into the cleaning solution [1]. The next soil is the particulate soil [1]. The particulate soil is typically found on the material to be cleaned and also in the wash to be redeposited [1]. Surfactants will also absorb onto the particulate [1]. Surfactants will not only suspend the particulates but they can help prevent the redeposition of the particulate soil back onto the substrate through charge repulsion by giving the soil a negative charge [1].
Now we will discuss the different types of surfactants and examples of each surfactant. Anionic surfactants are the most common surfactant due to low cost and ease of use and incorporation into detergent formulations [2]. The first surfactant was soap [1]. Soap is usually composed of fatty acids such as animal fat or vegetable oil with alkali [1,2]. . Next was alkyl benzene sulfonates but microbes could not break down the branched-chain alkyl benzene sulfonates [2]. The development of the anionic surfactants became more complex as new technology was developed to improve the performance of the surfactant [2]. In the table below, shows an illustration of how surfactants were developed from tallow soap to more complex surfactants such as Linear Alkylbenzene Sulfonate (LAS or LABS) and synthetic alcohol [1, 2].
[Taken from Reference 2]
LAS, or LABS, grew more complex and now the linearity of the alkyl chains range from 87% to 98% as seen in Figure below [3]. “While commercial LAS consists of more than 20 individual components, the ratio of the various homologues and isomers, representing different alkyl chain lengths and aromatic ring positions along the linear alkyl chain, is relatively constant in currently produced products, with the weighted average carbon number of the alkyl chain based on production volume per region between 11.7–11.8 has 10 to 14 carbons” [Taken from 3]
[Taken from Reference 3]
Anionic surfactants such as LAS are dissociate well in water, make excellent particulate-soil detergents, and have excellent detergency of natural fibers [2,4,5]. Since LAS is a low cost surfactant, LAS has become one of the most common used surfactant in the world in detergents [2, 4]. Some of the drawback of using LAS surfactants is that LAS surfactants are well known to be sequestered and precipitated from the wash solution by divalent cations under high water hardness conditions and thus reduces the cleaning power of the detergent [1]. This is one of the reasons that builders are used to soften the water which will be discussed later in the paper [1]. Another drawback is that LAS is not compatible with enzymes without stabilizers but LAS is compatible with hypochlorite bleach [2]. One route scientists have used to work around this issue is building longer LAS alcohols chains up to C14 -C18 [1]. Another benefit of LAS is that LAS helps with controlling foam and considered a foam stabilizer near neutral or basic pH ranges [4]. LAS have shown some foam control in the presence of lower levels of hardness and in the presence of oily soils [4]. Another anionic surfactant is alcohol sulfates [2, 4]. Alcohol sulfates are high foaming surfactant with excellent detergent properties, compatible with hypochlorite bleach, and hydrolyzes under acidic conditions [4]. Alcohol sulfates are sensitive to hard water and not compatible with enzymes without stabilizers [4]. Alcohol ether sulfates are very good detergents with high foaming surfactant, are milder and more hard water tolerant than LAS and alcohol sulfates, have greater compatibility with enzymes than LAS and alcohol sulfates and have greater versatility [4]. Alcohol ether sulfates are not compatible with hypochlorite bleach [2, 4].
Next surfactant is nonionic surfactants. They have been used in combination with anionic surfactants for many years to combine a boost in performance with keeping cost low [1]. This category of surfactants include alcohol ethoxylate [AE], alkylphenol ethoxylate [APE], methyl ester ethoxylate [MEE], ethoxylated amine, ethoxylated amide, alkyl polyglycoside [APG], polyethylene oxide-polyalkylene oxide diblock copolymer and many others [2, 5, 6]. Nonionic surfactants do not dissociate in solution, are good detergents in removing oily soil, excellent wetting agents, have good hard water tolerance and low to moderate foaming [2, 5, 6]. The most common nonionic surfactant is alcohol ethoxylate [AE]. An AE molecule is comprised of a fatty alcohol, which is ester-linked to polyethylene glycol or ethoxylate chain [5] and the general formula for AE is CH3–(CH2)x–O–(CH2CH2O)y–H [5]. Alcohol ethoxylate has shown that it has a better performance in cleaning the LAS and decent but not great foam control [6]. This is one of the reasons that AE is usually paired with an anionic surfactant typically LAS [1, 2, 6]. Nonionic surfactants are different from anionic surfactants in that the nonionic surfactants are not sensitive to hard water since no precipitation occurs in the presence of divalent ions, typically Ca+ and Mg+ [1, 2, 5, 6].
Next surfactant is the cationic surfactants. Majority of cationic surfactants used in detergent compositions are based on the nitrogen atom carrying positive charge [2]. “The most common cationic surfactants are the quaternary ammonium compounds with the general formula R’R”R’’’R’’’’, where X is usually chloride ion and R represents alkyl groups…, where R contains 8-18 C atoms,” [2]. The quaternary ammonium compounds are used due to the high antistatic activity and thus used as a common fabric softener [2]. It works by reducing the friction between fibers and between fibers and skin. It has been found that addition of certain cationic surfactants has exhibited improved soil and stain removal along with reducing the fading of dyes on colored fabrics [2]. Cationic surfactants will dissociate in water, have good emulsification properties, substantive to surfaces and fibers, have good antistatic properties and are unaffected by water hardness [2. 4, 6]
The last surfactant that is mentioned is amphoterics surfactants. Amphoterics surfactant contains both cationic and anionic groups [2]. Amphoteric surfactants will dissociate in water [2]. Amphoteric surfactants are generally moderate to high foamers, excellent oily soil and particulate detergents, and tolerate hard water better than the other surfactans [2]. Most common amphoteric surfactants are N-alkyl betaines such as laurylamidopropyldimethlybetaine. Amphoterics surfactant’s main characteristic is the ability to both cationic and anionic surfactant based on the solution the surfactant is dissolved in [2]. If the specific pH is acidic then the amphoteric surfactant become negatively charged and acts like anionic surfactant while if the specific pH is basic then the amphoteric surfactant becomes positively charged then acts like a cationic surfactant [2]. So this allows the amphoteric surfactants to be highly compatible with other surfactants and stable in both acidic and basic solutions. The detergency of amphoteric surfactants is better than of alcohol ethoxylate on oily soils and has better biodegradability [2, 5, 7]. However the amphoteric surfactants are mild and have lower skin and eye irritation when compared to anionic and nonionic surfactants [7].
III. Builders
Builders are called builders because they build the cleaning efficiency and effectiveness of detergent formulations [2]. Builders accomplish the goals of improving cleaning efficiency and effectiveness of detergent formulations by softening the water by binding the hard water minerals [Ca+ and Mg+ are the common minerals] [2, 8, 9, 10, 11] and thus controlling the water hardness [2,9,11]. Builders also help surfactants concentrate on removing soil from fabrics, increase the efficiency of the surfactant, provide a desirable level of alkaline to aid in the cleaning process, and disperse and suspend soils so they cannot redeposit onto the fabrics [2, 9, 11]. Builders have several water softening mechanisms such as sequestration/chelation, precipitation and ion exchange [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Builders can be organic or inorganic in nature [2]. The builder and metal ion form soluble complex such as polyphosphates, EDTA, and polyacrylates and will not interfere with the surfactants from interacting with the soil [2, 9, 11, 12, 13, 14, 15, 16, 17, 18] and thus increasing the efficiency of the surfactants. The builder can form a neutral salt with the metal ion and precipitate out of the solution [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Builder can also be not water soluble and sodium ions are substituted by hard water ions as in the case of zeolites and can sequester the metal ions out of the solution [12, 13]. Builders can act as chelating agents and react with metal ions by sharing electrons to form ringed structures, form highly stable complexes, and control metal ions in aqueous solutions [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Builders, as mentioned earlier, also have the ability to act as a buffer to keep the pH in a desired range to increase the efficiency of the surfactants [2]. Some of the more common builders are sodium carbonate, sodium silicate, sodium metasilicate, potassium silicate, sodium tripolyphosphate (STPP), zeolites A, sodium citrate, EDTA, sodium nitrilotriacetate, dipotassium phosphates, tetrapotassium pyrophosphate, potassium tripolyphosphate, phosphaonates such as Hydroxyethane-diphosphoric acid, and amino-tri(methylenephophonic acid) [9, 11, 12, 13, 14, 15, 16, 17, 18]. Most of these builders have either environmental issues, not biodegradable, or pose toxicity issues [2, 9, 11, 12, 13, 14, 15, 16, 17, 18]. Polyphosphates have been one of the more common since it has been an effective builder and have very lost cost but there are some environmental issues with phosphates [2, 8, 9, 10]. Polyphosphates tent to precipitate in higher temperatures and used as a softener because of the ability to chelate metal ions out of water very effectively. The environmental concern is that polyphosphates tend to cause eutrophication of waterways and tend to disturb the alkalinity of waterways and thus destroy the habitat of the water when in high concentration [9, 11, 12, 13, 14, 15, 16, 17, 18]. There has been several approaches to replacing the polyphosphates in detergents. Zeolites A have been explored. Zeolites show they can soften the water and demonstrate to not be toxic to the environment [12, 13]. Another substitute builder for polyphosphates is clinoptilolites of western Anatolia [14]. Clinoptilolites show that clinoptilolites can soften water and is comparable to polyphosphates at low temperature washing as a builder [14]. Sodium silicates have also been explored as another alternative to polyphosphate [15]. Amorphous silicate as a builder is comparative in softening water in proving that amorphous silicates have comparable calcium and magnesium tolerance [15]. Silicates as a co-builder in softening water at different temperatures have shown to be very soluble in water [15]. This is useful in assisting in preventing sludge in wastewater [15]. There are also polymeric builders [18]. The use of polyacrylic acid polymers and poly acrylic acid-co-maleic polymers as builders and co-builders to soften the water are being used [18]. They are being looked at as a replacement for polyphosphates in that they are reducing the amount of phosphates entering the waterway [18]. The problem with polymeric builders is that not all the polymers are biodegradable [18]. Research is being constantly done to create a more environmentally safe and more efficient builders to increase the efficiency of the builders and surfactants and increase the effectiveness of the detergents as a primary cleaner.
IV. Enzymes
Enzymes are a class of proteins present in all living organisms and are used as organic catalysts in such processes like digestion, glycolysis, etc. [19]. Enzymes catalyze a reaction and the reaction most interesting for detergents is hydrolysis [19]. The enzymes are used to break down the different stains and soils into smaller parts, surfactants need to be present to help solubilized the residues [19]. Enzymes are used in detergents to assist on enzyme sensitive stains such as egg yolk, spaghetti sauce, and organic soil [20]. Enzymes-containing products compromise more than 80% of the total laundry market [20]. There are several types of enzymes that are used in detergents. One of the more common enzymes for detergents is protease [21]. Proteases break down protein based soils such as blood, grass, and egg yolk [19, 21]. Another common enzyme for detergents is lipases. Lipases are used to break down fats and oils derived from animals or vegetables [19]. Another enzyme is amylase [19, 21]. Amylases are used to break down starches based on sugars such as chocolate and food syrups [19, 20, 21]. Another common enzyme is cellulose [21]. Cellulases are used to breakdown cellulose and remove microfibrils and polish fabrics [21]. Enzymes do break down and assist in removing soils but there are some drawbacks. Enzymes have a short shelf life [19, 20, 21]. They become inactivated in a short amount of time usually around 6 months or less [21]. Another drawback is that certain surfactants will cause surfactant-induced unfolding of the enzyme [19, 20, 21] and thus make the enzyme useless in the detergent.
V. Bleaches
Bleaches are chemicals that oxidize or reduce chemical bonds especially in unsaturated bonds that tend to be highly colored [2]. Bleach is used to decolorize stains and soils, kill microbes, and can be used to maintain whiteness [2]. There are two categories for the bleach and bleaching agents in cleaning detergents [2]. There are oxygen bleach and bleaching agents [2]. Oxygen bleach is used in the detergent oxide stains and remove soil. They can be either aqueous or dry [2]. “All dry oxygen bleaches contain inorganic peroxygen compounds, such as sodium perborate tetrahydrate and sodium percarbonate” [Taken from reference 2]. The oxygen bleach provides the detergent more of a gentle bleach cleaner that will decolorize or break up soil and organic materials during the cleaning application. Bleaching agents are used to make white clothes clean and keep them white [2]. The advantage is that this gives the detergent more cleaning power and better performance but the disadvantage is that this could have an effect on clothes with color and allow the colors to fade or be bleached out.
VI. Additives
Additives are chemicals that are added to give the detergent additional properties, smell, color, buffer, viscosity, and give a aesthetic improvement [2]. One property that is desired that an additive may help with is anti-redeposition [2]. Anti-Redeposition is to prevent soils and stains from redepositing onto the clean surfaces [2]. Anti-redeposition agents will help keep soils and stains suspended in the wash water so that it will not redeposit back on the fabrics or clean surfaces but go with the solution into the waste stream [2]. Several common anti-redeposition agent is anionic polymers, nonionic polymers, sodium polyacrylates, polyethylene glycol and polyacrylic acid [2, 18]. Another additive is a dispersant. Dispersant is used to suspend soils, particles, and metal ions for water hardness [2, 22]. Some builders could be used as a dispersant since they can suspend soils, particles and metal ions [2,21]. The suspension of metal ions will prevent the chemical from being an effective builder but may allow other builders and surfactants to be more effective in cleaning performance [2, 21]. Some additives may be used as buffer [2]. The additive may be used to maintain a certain pH that is optimal for the builder and surfactant to be an effective detergent in cleaning performance [2]. Some additive may be used as a corrosion inhibitor [2]. The additive may be used to prevent corrosion and oxidizing of the clean materials [2]. Some additives may be added to as a processing aid or as a co-polymer to keep the formulation homogenous [2]. Some additives are used as colorants for aesthetic improvement [2]. Fragrances can be added as an additive to improve the smell and create the desired odor [2]. Some additives are added for foam control [2]. Some additives are used as opacifiers to give the formulations a rich, viscous opaque appearance [2]. Other additives are used in specialized way such as optical brightners or a convenience to the customers [2].
VII. Conclusion
Home Care Detergents are composed of several different substances and all of the substances bring a unique property to the formulation. Surfactants are used as the primary cleaners in the formulation and are done at the surface or interface with the soil or stain [2]. Builders are used to build the cleaning efficiency and effectiveness of detergent formulations [2]. Enzymes may be used to break down the soils so that the surfactants can suspend the soil or stain. Bleaches used to decolorize stains and soils, kill microbes, and can be used to maintain whiteness [2]. Additives are chemicals that are added to give the detergent additional properties, smell, color, buffer, viscosity, and give a aesthetic improvement [2]. So each substance is used in the detergent to give the best cleaning performance.
VIII References:
[1] Baipal, Divya; Tyagi, V.K. [2007] "Laundry Detergents; An Overview" Journal of Oleo Science 56 [7] 327-340
DOI Link
[2] Scheibel, Jeffrey J. [2004] “The evolution of anionic surfactant technology to meet the requirements of the laundry detergent industry” Journal of Surfactants and Detergents 7 [4] 319-328 DOI Link
[3] Sanderson, Hans; Dyer, Scott D.; Price, Bradford B.; Nielsen, Allen M.; Compernolle, Remi van; Selby, Martin; Stanton, Kathleen; Evans, Alex; Ciarlo, Michael; Sedlak, Richard [2006] “Occurrence and weight-of-evidence risk assessment of alkyl sulfates, alkyl ethoxysulfates, and linear alkylbenzene sulfonates (LAS) in river water and sediments” Science of The Total Environment 368 [2-3] 695-712 DOI Link
[4] Zhang, Hui; Miller, Clarence A.; Garrett, Peter R.; Raney, Kirk H. [2005] “Lauryl alcohol and amine oxide as foam stabilizers in the presence of hardness and oily soil” Journal of Surfactants and Detergents 8 [1] 99-107 DOI Lilnk
[5] Belanger, S.E.; Dorn, P.B., Toy, R.; Boeije, G.; Marshall, S.J.; Wind,T.; Compernolle,, R. Van; Zeller, D. [2006] “Aquatic risk assessment of alcohol ethoxylates in North America and Europe” Ecotoxicology and Environmental Safety 64 [1] 85-99 DOI Link
[6] Tamura, Takamitsu; Iihara, Tadashi; Nishida, Shigeo; Ohta, Seiich [1999] “Cleaning Performance and Foaming Properties of Lauroylamidopropylbetaine/Nonionics Mixed Systems” Journal of Surfactants and Detergents 2 [2] 207-211 DOI Link
[7] Wolf M.D., Ronni; Parish M.D., Lawrence Charles [2012] “Effect of soaps and detergents on epidermal barrier function” Clinics in Dermatology 30 [3] 297-300 DOI Link
[8] Diamond, W.J. [1959] “The Effect of Temperature on the Phase Equilibrium of Polyphosphates” J. Phys. Chem 63 [1] 123-124 DOI Link
[9] Shen, C.Y.; Dyroff, D.R. [1966] “Hydrolyic Degradation of Sodium Tripolyphosphate in Concentrated Solutions and in Presence of Foreign Ions” Ind. Eng. Chem. Prod. Res. Dev. 5 [2] 97-100 DOI Link
[10] Scaffer, J.F.; Woodhams, R.T. [1977] “Polyelectrolyte Builders as Detergent Phosphate Replacements” Ind. Eng. Chem. Prod. Res. Dev. 16 [1] 3-11 DOI Link
[11] De Lucas, Antonio; Uguina, M. Angeles; Covian, Ignacio; Rodriguez, Lourdes [1992] “Synthesis of 13X zeolite from calcined koalins and sodium silicate for use in detergents” Ind. Eng. Chem. Res. 31 [9] 2134-2140 DOI Link
[12] Maki, Alan W.; Macek, Kenneth J. [1978] “Aquatic environmental safety assessment for a nonphosphate detergent builder” Environ. Sci. Technol. 12 [5] 573-580 DOI Link
[13] Costa, Enrique; De Lucas, Antonio; Uguina, M. Angeles; Ruiz, Juan Carlos [1988] “Synthesis of 4A zeolite from calcined kaolins for use in detergents” Ind. Eng. Chem. Res 27 [7] 1291-1296 DOI Link
[14] Çulfaz*, Müjgan; Saraçoğlu, Nurdan; Özdilek, Özlem [1996] “Clinoptilolites of western anatolia as detergent builders” Journal of Chemical Technology and Biotechnology 65 [3] 265-271 DOI Link
[15] De Lucas, Antonio; Rodriquez, Lourdes; Sanchez, Paula; Lobato, Justo [2000] “Synthesis of Crystalline Layered Sodium Silicate from Amorphous Silicate for Use in Detergents” Ind. Eng. Chem. Res. 39 [5] 1249-1255 DOI Link
[16] De Lucas, Antonio; Rodriquez, Lourdes, Sanchez, Paula; Carmona, Manuel; Romero, Pedro; Lobato, Justo [2004] “Comparative Study of the Solubility of the Crystalline Layered Silicates α-Na2Si2O5 and δ-Na2Si2O5 and the Amorphous Silicate Na2Si2O5” Ind. Eng. Chem. Res. 43 [6] 1472-1477 DOI LInk
[17] Matsumura, Shulchi; Nishioka, Makoto; Shigeno, Haruo; tanaka, Toshiyuki; Yoshikawa, Sadao [1993] “Builder performance in detergent formulations and biodegradability of partially dicarboxylated cellulose and amylose containing sugar residues in the backbone” Angew. Makromol. Chem 205 [1] 117-129 DOI Link
[18] Marholz, Thorsten; Klein, Joachim; Klein, Thomas [2002] “New Poly(sodium carboxylate)s Based on Saccharides, 1. Synthesis and Characterization of Ionic Allyl Glycoside Polymers” Macromolecular Chemistry and Physics 203 [18] 2640-2649 DOI Link
[19] Lund, Henrik, Kaasgaard, Svend Gunnar; Skagerlind, Peter; Jorgensen, Lene; Jorgensen, Christian Isak; van de Weert, Marco [2011] “Protease and Amylase Stability in the Presence of Chelators Used in Laundry Detergent Applications: Correlation Between Chelator Properties and Enzyme Stability in Liquid Detergents” Journal of Surfactants and Detergents 15 [3] 265-276 DOI Link
[20] Stoner, Michael R.; Dale, Douglas A.; Gualfetti, Peter J.; Becker, Todd; Manning, Mark C.; Carpenter, John F.; Randolph, Theodore W. [2004] “Protease autolysis in heavy-duty liquid detergent formulations: effects of thermodynamic stabilizers and protease inhibitors” Enzyme and Microbial Technology 34 [2] 114-125 DOI Link
[21] Stoner, Michael R.; Dale, Douglas A.; Gualfetti, Peter J. Becker, Todd; Randolph, Theodore W. [2006] “Surfactant-Induced Unfolding of Cellulase: Kinetic Studies” Biotechnology Progress 22 [1] 225-232 DOI Link
[22] Strauss, Ulrich P.; Treitler, Theodore L. [1955] “Chain Branching in Glassy Polyphosphates: Dependence on the Na/P Ratio and Rate of Degradation at 25°“J. Am Chem Soc. 77 [6] 1473-1476 DOI Link